Understanding brewing trait inheritance in Lager yeast hybrids.

UNLABELLED

Hybridization between and resulted in the emergence of , a crucial yeast for lager fermentation. However, our understanding of hybridization success and hybrid vigor between these two species remains limited due to the scarcity of parental strains. Here, we explore hybridization success and the impact of hybridization on fermentation performance and volatile compound profiles in newly formed lager hybrids. By selecting parental candidates spanning a diverse array of lineages from both species, we reveal that the Beer and PB-2 lineages exhibit high rates of hybridization success in and , respectively. Polyploid hybrids were generated through a spontaneous diploid hybridization technique (rare-mating), revealing a prevalence of triploids and diploids over tetraploids. Despite the absence of heterosis in fermentative capacity, hybrids displayed phenotypic variability, notably influenced by maltotriose consumption. Interestingly, ploidy levels did not significantly correlate with fermentative capacity, although triploids exhibited greater phenotypic variability. The parental lineages primarily influenced volatile compound profiles, with significant differences in aroma production. Interestingly, hybrids emerging from the Beer parental lineages exhibited a volatile compound profile resembling the corresponding parent. This pattern may result from the dominant inheritance of the aroma profile, as suggested by the over-expression of genes related to alcohol metabolism and acetate synthesis in hybrids including the Beer lineage. Our findings suggest complex interactions between parental lineages and hybridization outcomes, highlighting the potential for creating yeasts with distinct brewing traits through hybridization strategies.

IMPORTANCE

Our study investigates the principles of lager yeast hybridization between and . This process gave rise to the lager yeast . By examining how these novel hybrids perform during fermentation and the aromas they produce, we uncover the genetic bases of brewing trait inheritance. We successfully generated polyploid hybrids using diverse strains and lineages from both parent species, predominantly triploids and diploids. Although these hybrids did not show improved fermentation capacity, they exhibited varied traits, especially in utilizing maltotriose, a key sugar in brewing. Remarkably, the aroma profiles of these hybrids were primarily influenced by the parent, with Beer lineage hybrids adopting aroma characteristics from their parent. These insights reveal the complex genetic interactions in hybrid yeasts, opening new possibilities for crafting unique brewing yeasts with desirable traits.